Summary: Access the authentication and encryption features provided by GnuPG

Enigmail is an extension to the mail client of Mozilla Thunderbird
which allows users to access the authentication and encryption
features provided by GnuPG.
Main Features
* Encrypt/sign mail when sending, decrypt/authenticate received
mail
* Support for inline-PGP (RFC 2440) and PGP/MIME (RFC 3156)
* Per-Account based encryption and signing defaults
* Per-Recipient rules for automated key selection, and
enabling/disabling encryption and signing
* OpenPGP key management interface